In a typical cellular radio system, wireless terminals (also known as mobile stations and/or user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks. The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” (UMTS) or “eNodeB” (LTE). A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on is radio frequencies with the user equipment units (UE) within range of the base stations.
In some versions of a radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a controller node (such as a radio network controller (RNC) or a base station controller (BSC)) which supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). UTRAN is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. Specifications for the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) are ongoing within the 3rd Generation Partnership Project (3GPP). The Evolved Universal Terrestrial Radio Access Network (E-UTRAN) comprises the Long Term Evolution (LTE) and System Architecture Evolution (SAE). Long Term Evolution (LTE) is a variant of a 3GPP radio access technology where the radio base station nodes are connected directly to a core network rather than to radio network controller (RNC) nodes. In general, in LTE the functions of a radio network controller (RNC) node are distributed between the radio base stations nodes (eNodeB's in LTE). As such, the radio access network (RAN) of an LTE system has an essentially “flat” architecture comprising radio base station nodes without reporting to radio network controller (RNC) nodes.
It is desirable that a wireless network be simple to deploy and cost efficient to operate. There is also current interest in having the network be self-organizing where possible. Furthermore, good coverage is important for a mobile broadband experience—both outdoors and indoors. But changes in a wireless environment affect the quality of signal transmitted and received, and reception power rapidly decreases in proportion to increasing distance between wireless communication entities. As a result, a wireless communication system may employ a relay node, repeater station, or the like to expand coverage and/or improve throughput, quality, etc. The term “relay node” (RN) is used hereafter to encompass relays, repeaters, and similar radio access network nodes that are directly connected to a base station either wirelessly, by wire, or by optical fiber. A relay node may use radio communications technology both for communicating user data between a mobile terminal and the relay node over the radio interface and for the transport connection between the relay node and a base station.
Although a relay node may be less sophisticated, expensive, and intelligent than a regular base station (BS), NodeB, eNodeB, or access point (AP), a relay node stills performs some of the same functions as a base station. The term “donor base station” is used to identify the base station that the relay node is currently using to connect to the backhaul network. A relay node performs an “amplify and forward” (AF) function where it amplifies a signal received from a BS/AP or a MS/UE and delivers the amplified signal to the MS/UE or the BS/AP. Some relays may perform a decoding and forward (DF) function as well as a scheduling function where communicated information is restored by performing demodulation and decoding on a signal received from the BS/AP or the MS/UE and generating the restored signal by performing coding and modulation which is then sent to the MS/UE or the BS/AP.
Radio access networks typically include some sort of network management node to support configuration, equipment management, fault management, performance management, etc. For example, in the 3G Long Term Evolution (LTE) system, base stations called eNodeBs are managed by a domain manager (DM), also referred to as an operation and support system (OSS). Sometimes the individual eNodeBs (eNBs) are handled by an element manager (EM), which is a part of the domain manager. A domain manager typically only manages equipment from the same vendor. Domain manager tasks include configuration of the network elements, fault management, and performance monitoring.
In performing operations and maintenance (O&M) functions like fault management and performance monitoring, significant amounts of data from events and counters are regularly transferred from the eNBs up to the domain manager. For relay nodes, one challenge with O&M architectures, e.g., like the O&M architecture in LTE, is the timing of transporting O&M data, such as fault and performance data in the form for example of counter values and events, over the radio interface. The transport of O&M data is triggered by the domain manager or when an event occurs, which means that the time of transport is typically not aligned with the radio resource management of the donor base station often putting an unnecessary strain on those resources at that time.
Another problem is that a relay node may be unavailable at times, for example due to inactivity and energy efficiency actions, or because the relay node is being relocated. During such times, the O&M system is unable to contact the relay node to acquire fault and performance data or to send configuration information. Moreover, neighboring base stations are unable to send configuration information requests to the relay node.
Yet another problem with typical O&M architectures is that the relay node may change its donor base station over time. As a result, information about the relay node in the source donor base station must be provided to and stored in the target donor base station. It would be desirable to have an efficient way to provide such relay node information to the target donor base station that does not necessarily involve the relay node.